SALT TEST 289 



Hence, 



58. 5 grams salt combine with 170 grams sil\'er nitrate. 



I gram salt combines with -— — = 2 . 906 grams silver nitrate, 



58-5 

 or 



.01 gram salt combines with .02906 gram silver nitrate. 



Features of Practical Salt Tests. — The same principle applies 

 to the various salt tests. In the different practical tests, com- 

 binations are worked out which enable us to read the per cent of 

 salt directly, without having to make any mathematical calcu- 

 lations. 



The following combination enables us to read the per cent 

 of salt in butter directly: 



\i) 29.06 (^ = 29.0) grams of silver nitrate in a solution made 

 up to 1000 c.c. 



(2) Burette for silver nitrate soluti<jn graduated in cubic 

 centimeters and tenths of a cubic centimeter. 



(3) 10 grams of butter, with the salt solution from it made up 

 to 250 c.c. 



(4) 25 c.c. of the salt solution, taken by means of a 25 c.c. 

 pipette, that is, a tenth of the salt solution, or a tenth of the salt 

 in the lo-gram sample of butter. 



In 1000 c.c. of silver nitrate solution there are 29.06 grams of 

 silver nitrate. 



In I c.c. of silver nitrate solution there is .02906 gram silver 

 nitrate. 



But we have already shown that .02906 gram silver nitrate 

 reacts with .01 gram of salt. 



.01 gram salt in 25 c.c. salt solution = .i gram salt in 250 c.c. 

 of salt solution, or in 10 grams butter, which is i per cent 

 of salt. 



Hence, each cubic centimeter of the silver nitrate solution 

 required in making the test indicates i.o per cent of salt in 

 the Imtter. 



